body{
    margin: 0;
}
a {
    text-decoration: none;
    color:black;
}
/*正常的未被访问过的链接*/
a:link {
    text-decoration: none;
}
/*已经访问过的链接*/
a:visited {
    text-decoration: none;
}
/*鼠标划过(停留)的链接*/
a:hover {
    text-decoration: none;
}
/* 正在点击的链接*/
a:active {
    text-decoration: none;
}